I have to say only good things about StockXpert. Really. That site looks good, they tested the site engine on a free site,
www.sxc.hu. (I'm not sure 100% that this is true, but sxp is very similar to sxc).
Even if sxp has less photos than other well-known sites, I have good traffic and enough good sales. I think, that the main success of sxp is it's 'brother' free site that has a high traffic and sxp is promoted from there.
By the way, sxc is a powerful resource for designers, beside the noisy photos they have also a lot of technically good shoots. Last month I discovered somebody who does know only about sxc, he was no member of commercial stock photo communities.